Our research efforts will attempt to define the mechanism(s) of disease pathogenesis of trichomonal vaginitis through identification and characterization of virulence determinants. Optimal growth conditions will be established and physiologic parameters will be evaluated for their effect on expression or modulation of membrane protein markers and/or pathogenicity. The interaction of virulent Trichomonas vaginalis with host cell surfaces will be investigated using cell culture systems, and studies identifying potential ligands on trichomonal surfaces for host cells will be initiated. Contact-dependent versus independent cytopathogenic mechanisms will be evaluated microscopically using brightfield, darkfield, and interference-contract optics. The protein composition and surface characterization of intact trichomonads and of trichomonad plasma membrane preparations will be performed for identification of highly immunogenic and exposed proteins. Laboratory animals will be evaluated as models for establishment of subcutaneous, intravaginal, and intraperitoneal infections. Immune (IgG) responses to specific antigens will be monitored in animals following infection or vaccination with whole T. vaginalis or membrane preparations. Numerous isolates of pathogenic T. vaginalis along with an avirulent strain and trichomonads sensitive and resistant to metronidazole will be used in this study. Clone isolation of each strain will be accomplished, and colonies will be analyzed for cytopathogenicity, surface protein composition, host protein acquisition, and virulence. The latter will be determined by the ability of trichomonads to establish infection in laboratory animals. Future research dealing with the purification and characterization of extracellular products such as proteases as well as studies of the selective and avid association of specific host proteins with the surfaces of T. vaginalis is anticipated. The knowledge from these studies will be applied to other pathogenic trichomonal species as well as other protozoan infestations.